Why Shouldn’t Septic Leach Fields Be Installed Under Driveways, Roads, And Impervious Surfaces?

When wastewater from a septic tank enters the leach field, it percolates through the soil and is treated by microorganisms that break down and remove harmful contaminants. If the soil has an impervious surface placed above it it will reduce that ability to percolate through the soil. With the soil compacted the soil surrounding the leach field is unable to absorb the water because the once open pores are compressed and compacted. This will cause leach field failure as the water is unable to dissipate into the soil.  

A Leach Field can show signs of a Failing septic system, which wouldn’t be possible if it were installed under an impervious surface.

A leach field should be installed in a field in which percolation testing will determine the size, type, and location of your leach field.

The secondary effect of the presence of an impervious layer is lack of “evapotranspiration” in the leach field area. Evapotranspiration is the process by which water is transferred from the land to the atmosphere by evaporation from the soil and other surfaces and by transpiration from plants.  Evapotranspiration aids to manage and disperse treated wastewater into the atmosphere. This natural process aids in the disposal and absorption of effluent from septic systems, contributing to the overall efficiency of wastewater treatment in on-site sewage systems. With the addition of an impervious surface above the leach field  “evapotranspiration”  cannot occur and restricts the leach field performance. 

Therefore, it is important to locate the leach field in an area with suitable soil conditions and sufficient space to ensure proper treatment and disposal of wastewater. It should be located away from any potential sources of contamination and not placed under any impervious surfaces or areas with heavy traffic.

Failed Septic Field could show signs of leak